1. Field of the Invention
This invention relates to a photosensitive resin composition, and more specifically, to a photosensitive resin composition which is cured by irradiation with actinic rays and provides visible contrast between the exposed and unexposed area.
2. Description of the Prior Art
Preferably a photosensitive material such as a photosensitive printing plate (also known as a presensitized plate and hereinafter abbreviated PS plate) or a photo resist is capable of providing a print-out image, or the exposed area can be visually distinguished prior to development. Take for example of the PS plate, it is often subjected to photo composing, step and repeat printing down, where the ability to provide a print-out image is very important because the inability to recognize the exposed portion makes it difficult to perform the subsequent exposures. Research Disclosure No. 157, pp. 50-54, May 1977 discloses a PS plate using a photosensitive resin composition which is able to provide a printout image by use of a combination of a leuco dye and an organic azide compound. However, given the print-out effect, this PS plate has reduced sensitivity and, after storage, the plate gives only a dull print-out image.
Therefore, attempts have been made to provide a photosensitive resin composition with a print-out effect using the print-out compositions described in U.S. Pat. Nos. 3,106,466, 3,113,024, 3,121,633, 3,954,475, and 3,987,037. However, the resulting resin compositions either have low sensitivity or provided a dull print-out image after storage even when they have satisfactory sensitivity.